Effects of different disturbance types on butterflyfish communities of Australia's Great Barrier Reef

Abstract

The effects of disturbances on coral reef fishes have been extensively documented but most studies have relied on opportunistic sampling following single events. Few studies have the spatial and temporal extent to directly compare the effects of multiple disturbances over a large geographic scale. Here, benthic communities and butterflyfishes on 47 reefs of the Great Barrier Reef were surveyed annually to examine their responses to physical disturbances (cyclones and storms) and/or biological disturbances (bleaching, outbreaks of crown-of-thorns starfish and white syndrome disease). The effects on benthic and butterflyfish communities varied among reefs depending on the structure and geographical setting of each community, on the size and type of disturbance, and on the disturbance history of that reef. There was considerable variability in the response of butterflyfishes to different disturbances: physical disturbances (occurring with or without biological disturbances) produced substantial declines in abundance, whilst biological disturbances occurring on their own did not. Butterflyfishes with the narrowest feeding preferences, such as obligate corallivores, were always the species most affected. The response of generalist feeders varied with the extent of damage. Wholesale changes to the butterflyfish community were only recorded where structural complexity of reefs was drastically reduced. The observed effects of disturbances on butterflyfishes coupled with predictions of increased frequency and intensity of disturbances sound a dire warning for the future of butterflyfish communities in particular and reef fish communities in general.